#app1{
    width: 50vw;
    height: 50vh;
    display: flex;
    justify-content: center;
    align-items: center;
}
#app1 .output{
    position: absolute;
    top: 15vh;
    font-size: 30px;
}
#app1 button{
    margin-right: 10px;
    max-width: 50px;
    max-height: 50px;
    padding: 5px 8px;
}